Semiconductor storage device and electronic apparatus

ABSTRACT

A semiconductor storage device includes a plurality of memory macros including a plurality of memory cell arrays; a low-potential power supply boosting circuit coupling the low-potential power supply to the ground in a normal mode and coupling the low-potential power supply to a voltage higher than a ground voltage in a sleep mode; a virtual power control circuits including a plurality of switches which is turned on when switching from the sleep mode to the normal mode and is turned off when switching from the normal mode to the sleep mode; and a sleep cancellation detecting circuit outputting, when the mode control signal supplied to the plurality of switches in one of the plurality of memory macros indicates to switch form the sleep mode to the normal mode, the mode control signal to a subsequent memory macro subsequent to the one of the plurality of memory macros.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.12/695,641, filed Jan. 28, 2010, which claims the benefit of priorityfrom Japanese Patent Application No. 2009-17798 filed on Jan. 29, 2009and Japanese Patent Application No. 2009-227306 filed on Sep. 30, 2009,the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

Embodiments discussed herein relates to a semiconductor storage device.

2. Description of Related Art

To save power consumption, a sleep mode is set when a semiconductorstorage device is in a standby state. In the sleep mode, a power supplyvoltage supplied to the semiconductor storage device decreases from thevoltage level for a normal operation (normal mode).

A related technology is disclosed in, for example, Japanese Laid-openPatent Publication No. 2008-226384.

SUMMARY

According to one aspect of the embodiments, a semiconductor storagedevice is provided which includes: a plurality of memory macros coupledin series, each of the plurality of memory macros including a pluralityof memory cell arrays; a low-potential power supply boosting circuitprovided for each of the plurality of memory cell arrays, thelow-potential power supply boosting circuit provided between alow-potential power supply and a ground, the low-potential power supplyboosting circuit being configured to couple the low-potential powersupply to the ground in a normal mode and couple the low-potential powersupply to a voltage higher than a ground voltage in a sleep mode; avirtual power control circuits provided for each of the plurality ofmemory cell arrays, the virtual power control circuit including aplurality of switches provided in parallel with the low-potential powersupply boosting circuit, the plurality of switches being configured tobe turned on when a mode control signal indicates to switch from thesleep mode to the normal mode and configured to be turned off when themode control signal indicates to switch from the normal mode to thesleep mode; and a sleep cancellation detecting circuit configured tooutput, when the mode control signal supplied to the plurality ofswitches of one of the plurality of memory arrays in one of theplurality of memory macros indicates to switch form the sleep mode tothe normal mode, the mode control signal to a subsequent memory macrosubsequent to the one of the plurality of memory macros.

Additional advantages and novel features of the invention will be setforth in part in the description that follows, and in part will becomemore apparent to those skilled in the art upon examination of thefollowing or upon learning by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary semiconductor storage device.

FIG. 2 illustrates an exemplary memory macro.

FIG. 3 illustrates an exemplary virtual power control circuit.

FIG. 4 illustrates an exemplary switching operation from a sleep mode toa normal mode.

FIG. 5 illustrates an exemplary memory macro.

FIG. 6 illustrates an exemplary memory macro.

FIG. 7 illustrates an exemplary semiconductor device.

FIG. 8 illustrates an exemplary memory macro.

FIG. 9 illustrates an exemplary memory macro.

FIG. 10 illustrates an exemplary semiconductor device.

FIG. 11 illustrates an exemplary memory macro.

FIG. 12 illustrates an exemplary delay circuit.

FIG. 13 illustrates an exemplary delay circuit.

DESCRIPTION OF EMBODIMENTS

In a normal mode, when data is written to a memory cell or data is readfrom a memory cell, a power supply voltage to a semiconductor storagedevice may decrease. To address the decrease in power supply voltage, apower supply voltage for preventing data stored in a memory cell frombeing erased, for example, a normal power supply voltage, is supplied tothe semiconductor storage device.

In a sleep mode, outside input is blocked, and bit lines or word lines(not illustrated) in memory cells are not selected. A minimal powersupply voltage that prevents data stored in a memory cell from beingerased, for example, a minimum power supply voltage, is supplied to thesemiconductor storage device.

Quick switching from the sleep mode to the normal mode may cause anincrease in return current that reduces the power supply voltage, anddata stored in a memory cell may disappear.

Switching from the sleep mode to the normal mode allows wiring of thesemiconductor storage device or a capacitance component of a circuit tobe charged to the normal power supply voltage. Quick switching from thesleep mode to the normal mode may cause return current to flow duringcharging.

A plurality of transistors coupled in parallel between memory cellarrays and a ground are turned on in sequence. Since the conductanceincreases stepwise, a current flows stepwise. The time interval forswitching from the sleep mode to the normal mode may be increased, andthe maximum value of return current may be reduced.

In a semiconductor storage device having a plurality of memory macroseach including a plurality of memory cell arrays, the plurality ofmemory macros may be switched contemporaneously in response to a signalfor switching from the sleep mode to the normal mode.

FIG. 1 illustrates an exemplary semiconductor storage device. Asemiconductor storage device 10 includes a normal mode and a sleep mode.A first sleep signal SLP1 for setting the normal mode or the sleep modemay be input from an external device (not illustrated). In response tothe first sleep signal SLP1, the semiconductor storage device 10 is setto the normal mode or the sleep mode.

The semiconductor storage device 10 is set to the normal mode inaccordance with a high-level first sleep signal SLP1. The semiconductorstorage device 10 is set to the sleep mode in accordance with alow-level first sleep signal SLP1.

The semiconductor storage device 10 includes first to fourth memorymacros 11 to 14. FIG. 2 illustrates an exemplary memory macro. Thememory macro illustrated in FIG. 2 may be the first memory macro 11illustrated in FIG. 1. Referring to FIG. 2, the first memory macro 11includes a drive circuit 17, first to n-th memory cell array units M1 toMn, and a sleep cancellation detecting circuit 18.

The drive circuit 17 includes a first inverter circuit 20 a and a secondinverter circuit 20 b, which are coupled in series. The drive circuit 17receives a first sleep signal SLP1 from, for example, an external device(not illustrated). The drive circuit 17 improves the drive performanceof the first sleep signal SLP1 to obtain a driven sleep signal SLPd, andoutputs the driven sleep signal SLPd to the first to n-th memory cellarray units M1 to Mn and the sleep cancellation detecting circuit 18.

Each of the memory cell array units M1 to Mn includes a virtual powercontrol circuit 23, a memory cell array 24, and a low-potential powersupply boosting circuit. The low-potential power supply boosting circuitmay include an N-channel metal oxide semiconductor (MOS) transistor T1.The virtual power control circuit 23 controls the voltage level of avirtual power supply line LK. The virtual power supply line LK may be alow-potential power supply line of the memory cell array 24. In thenormal mode, the virtual power control circuit 23 couples the virtualpower supply line LK to a ground potential GND. The memory cell array 24is supplied with a power supply voltage Vcc as a high-potential powersupply voltage and is supplied with the ground potential GND as alow-potential power supply voltage. In the sleep mode, the virtual powercontrol circuit 23 controls the voltage level of the virtual powersupply line LK to a threshold voltage of the N-channel MOS transistorT1. The memory cell array 24 is supplied with the power supply voltageVcc as a high-potential power supply voltage and is supplied with thethreshold voltage of the N-channel MOS transistor T1 as a low-potentialpower supply voltage.

In the sleep mode, the memory cell array 24 operates at a voltage thatis lower than that in the normal mode by an amount corresponding to thethreshold voltage of the N-channel MOS transistor T1, resulting in lowerpower consumption.

FIG. 3 illustrates an exemplary virtual power control circuit. Thevirtual power control circuit illustrated in FIG. 3 may be the virtualpower control circuit 23 provided in the first memory cell array unit M1illustrated in FIG. 2. In the virtual power control circuit 23 providedin the first memory cell array unit M1, a third delayed sleep signalSLPt3 is output to the sleep cancellation detecting circuit 18. Otherconfiguration is substantially the same as or similar to that of thevirtual power control circuits 23 provided in the second to n-th memorycell array units M2 to Mn.

The virtual power control circuit 23 provided in the first memory cellarray unit M1 includes first to fourth transistors Ta to Td and first tothird delay circuits 31 to 33. The first to fourth transistors Ta to Tdmay include an N-channel MOS transistor, and the transistor sizes of thefirst to fourth transistors Ta to Td may increase in this order.

The driven sleep signal SLPd output from the drive circuit 17 issupplied to the gate of the first transistor Ta, and is also supplied tothe first delay circuit 31. The drain of the first transistor Ta iscoupled to the virtual power supply line LK of the memory cell array 24,and the source of the first transistor Ta is coupled to the groundpotential GND. In accordance with the driven sleep signal SLPd outputfrom the drive circuit 17, the first transistor Ta connects ordisconnects the virtual power supply line LK and the ground potentialGND.

Upon receipt of a high-level driven sleep signal SLPd indicating, forexample, the normal mode, the first transistor Ta is turned on andcouples the virtual power supply line LK and the ground potential GND.Upon receipt of a low-level driven sleep signal SLPd indicating, forexample, the sleep mode, the first transistor Ta is turned off anddisconnects the virtual power supply line LK and the ground potentialGND.

The first delay circuit 31 includes a first inverter circuit 35 a and asecond inverter circuit 35 b, which are coupled in series. The firstdelay circuit 31 delays the driven sleep signal SLPd output from thedrive circuit 17 by a delay time t1 to obtain a first delayed sleepsignal SLPt1, and outputs the first delayed sleep signal SLPt1 to thegate of the second transistor Tb and the second delay circuit 32.

The drain of the second transistor Tb is coupled to the virtual powersupply line LK, and the source of the second transistor Tb is coupled tothe ground potential GND. The first delayed sleep signal SLPt1 outputfrom the first delay circuit 31 is supplied to the gate of the secondtransistor Tb. In accordance with the first delayed sleep signal SLPt1output from the first delay circuit 31, the second transistor Tbconnects or disconnect the virtual power supply line LK and the groundpotential GND.

The second transistor Tb is turned on and off behind the delay time t1from the turn-on/off timing of the first transistor Ta. In accordancewith a high-level first delayed sleep signal SLPt1 indicating, forexample, the normal mode, the second transistor Tb is turned on andcouples the virtual power supply line LK and the ground potential GND.In accordance with a low-level first delayed sleep signal SLPt1indicating, for example, the sleep mode, the second transistor Tb isturned off and disconnects the virtual power supply line LK and theground potential GND.

The second delay circuit 32 includes a first inverter circuit 36 a and asecond inverter circuit 36 b, which are coupled in series. The seconddelay circuit 32 delays the first delayed sleep signal SLPt1 output fromthe first delay circuit 31 by the delay time t1 to obtain a seconddelayed sleep signal SLPt2, and outputs the second delayed sleep signalSLPt2 to the gate of the third transistor Tc and the third delay circuit33.

The drain of the third transistor Tc is coupled to the virtual powersupply line LK, and the source of the third transistor Tc is coupled tothe ground potential GND. The second delayed sleep signal SLPt outputfrom the second delay circuit 32 is supplied to the gate of the thirdtransistor Tc. In accordance with the second delayed sleep signal SLPt2output from the second delay circuit 32, the third transistor Tcconnects or disconnects the virtual power supply line LK and the groundpotential GND.

The third transistor Tc is turned on and off behind the delay time t1from the turn-on/off timing of the second transistor Tb. The thirdtransistor Tc is turned on and off behind a delay time t2 (=2×t1) fromthe turn-on/off timing of the first transistor Ta.

In accordance with a high-level second delayed sleep signal SLPt2indicating, for example, the normal mode, the third transistor Tccouples the virtual power supply line LK and the ground potential GND.In accordance with a low-level second delayed sleep signal SLPt2indicating, for example, the sleep mode, the third transistor Tcdisconnects the virtual power supply line LK and the ground potentialGND.

The third delay circuit 33 includes a first inverter circuit 37 a and asecond inverter circuit 37 b, which are coupled in series. The thirddelay circuit 33 delays the second delayed sleep signal SLPt2 outputfrom the second delay circuit 32 by the delay time t1 to obtain a thirddelayed sleep signal SLPt3, and outputs the third delayed sleep signalSLPt3 to the gate of the fourth transistor Td.

The drain of the fourth transistor Td is coupled to the virtual powersupply line LK, and the source of the fourth transistor TD is coupled tothe ground potential GND. The third delayed sleep signal SLPt3 outputfrom the third delay circuit 33 is supplied to the gate of the fourthtransistor Td. In accordance with the third delayed sleep signal SLPt3output from the third delay circuit 33, the fourth transistor Tdconnects or disconnects the virtual power supply line LK and the groundpotential GND.

The fourth transistor Td is turned on and off behind the delay time t1from the turn-on/off timing of the third transistor Tc. The fourthtransistor Td is turned on and off behind a delay time t3 (=3×t1) fromthe turn-on/off timing of the first transistor Ta.

The delay time t3 represents the time period, for example, beginningfrom the time when the first memory macro 11 starts switching from thesleep mode to the normal mode to the time when the first to fourthtransistors Ta to Td are turned on so that the return current flowingduring the switching becomes maximum.

In accordance with a high-level third delayed sleep signal SLPt3indicating, for example, the normal mode, the fourth transistor Tdcouples the virtual power supply line LK and the ground potential GND.In accordance with a low-level third delayed sleep signal SLPt3indicating, for example, the sleep mode, the fourth transistor Tddisconnects the virtual power supply line LK and the ground potentialGND.

The virtual power control circuit 23 causes a high-level driven sleepsignal SLPd output from the drive circuit 17 to be sequentially delayedusing the first to third delay circuits 31 to 33. Consequently, thesecond to fourth transistors Tb to Td are turned on with the delay timest1, t2 (=2×t1), and t3 (=3×t1), respectively, so that the virtual powersupply line LK and the ground potential GND are coupled.

The virtual power control circuit 23 causes the first to fourthtransistors Ta to Td to be sequentially turned on when the sleep mode isswitched to the normal mode, thereby causing the conductance to increasestepwise to facilitate current flow from the virtual power supply lineLK to the ground potential GND.

The virtual power control circuit 23 decreases stepwise the voltagelevel of the virtual power supply line LK to the ground potential GNDduring the switching from the sleep mode to the normal mode. A stepwiseincrease from the minimum power supply voltage for the sleep mode to thenormal power supply voltage for the normal mode (which is greater thanthe minimum power supply voltage) results in an increase in theswitching time. Thus, the maximum value of return current is reduced.

The memory cell array 24 in the first memory cell array unit M1 includesa plurality of memory cells arranged in a matrix (not illustrated). Thememory cells store data of “1” or “0”, and the data is written into thememory cells or is read from the memory cells. The power supply voltageVcc and the voltage of the virtual power supply line LK are supplied toeach of the memory cells as a high-potential power supply voltage and alow-potential power supply voltage, respectively.

In the first memory cell array unit M1, the drain and gate of theN-channel MOS transistor T1 are coupled to the virtual power supply lineLK of the memory cell array 24. The source of the N-channel MOStransistor T1 is coupled to the ground potential GND. In accordance withthe operation of the virtual power control circuit 23, the N-channel MOStransistor T1 connects or disconnects the virtual power supply line LKand the ground potential GND.

When the virtual power control circuit 23 disconnects the virtual powersupply line LK and the ground potential GND, a standby current for thesleep mode is supplied from the memory cell array 24. Thus, the gatevoltage of the N-channel MOS transistor T1 in the first memory cellarray unit M1 is set around the threshold voltage, and the N-channel MOStransistor T1 is turned on. The voltage level of the virtual powersupply line LK may become substantially equal to the threshold voltageof the N-channel MOS transistor T1.

When the virtual power control circuit 23 couples the virtual powersupply line LK and the ground potential GND, the drain and gate of theN-channel MOS transistor T1 are coupled to the ground potential GND.Thus, the N-channel MOS transistor T1 is turned off. The voltage levelof the virtual power supply line LK may become substantially equal tothe ground potential GND.

The N-channel MOS transistor T1 may be turned on in the sleep mode, andthe voltage level of the corresponding virtual power supply line LK maybecome close to the threshold voltage of the N-channel MOS transistorT1. The N-channel MOS transistor T1 may be turned off in the normalmode, and the voltage level of the corresponding virtual power supplyline LK may become substantially equal to the ground potential GND.

In each of the second to n-th memory cell array units M2 to Mn, thethird delayed sleep signal SLPt3 output from the third delay circuit 33is not output to the sleep cancellation detecting circuit 18. Otherconfiguration may be substantially the same as or similar to theconfiguration of the first memory cell array unit M1.

In the first to n-th memory cell array units M1 to Mn, the first tofourth transistors Ta to Td included in the virtual power controlcircuits 23 may be turned on and off at substantially the same time. Thethird delayed sleep signal SLPt3, which notifies that the first tofourth transistors Ta to Td included in the virtual power controlcircuit 23 in each of the memory cell array units M1 to Mn have beenturned on, is output from the virtual power control circuit 23 in thefirst memory cell array unit M1.

The sleep cancellation detecting circuit 18 illustrated in FIG. 2includes a NAND circuit 40 and an inverter circuit 41. The driven sleepsignal SLPd output from the drive circuit 17 and the third delayed sleepsignal SLPt3 output from the virtual power control circuit 23 in thefirst memory cell array unit M1 behind the delay time t3 from the drivensleep signal SLPd are input to the NAND circuit 40. When the inputdriven sleep signal SLPd and third delayed sleep signal SLPt3 are at ahigh level, the NAND circuit 40 outputs a low-level control completionsignal Sk to the inverter circuit 41.

The inverter circuit 41 inverts the control completion signal Sk outputfrom the NAND circuit 40 to obtain a second sleep signal SLP2, andoutputs the second sleep signal SLP2 to the second memory macro 12.

When the first to fourth transistors Ta to Td of the virtual powercontrol circuits 23 included in the first to n-th memory cell arrayunits M1 to Mn are turned on, the sleep cancellation detecting circuit18 outputs a high-level second sleep signal SLP2 indicating, forexample, the normal mode in accordance with a high-level third delayedsleep signal SLPt3 output from the virtual power control circuit 23 inthe first memory cell array unit M1.

When the first to fourth transistors Ta to Td of the virtual powercontrol circuits 23 included in the first to n-th memory cell arrayunits M1 to Mn are turned off, the sleep cancellation detecting circuit18 outputs a low-level second sleep signal SLP2 in accordance with alow-level driven sleep signal SLPd output from the drive circuit 17.

When the time period from when the first memory cell array unit M1starts switching from the sleep mode to the normal mode to when thefirst to fourth transistors Ta to Td are turned on so that the returncurrent is maximized, for example, the delay time t3 (=3×t1), haselapsed, the sleep cancellation detecting circuit 18 outputs ahigh-level second sleep signal SLP2 indicating, for example, the normalmode to the second memory macro 12. In accordance with the second sleepsignal SLP2, the second memory macro 12 starts switching from the sleepmode to the normal mode.

The configuration of the second to fourth memory macros 12 to 14 may besubstantially the same as or similar to the configuration of the firstmemory macro 11.

FIG. 4 illustrates an exemplary switching operation from a sleep mode toa normal mode. The switching operation illustrated in FIG. 4 may beperformed by the semiconductor storage device 10 illustrated in FIG. 1.At time tk0, the semiconductor storage device 10 is set to the sleepmode in accordance with a low-level first sleep signal SLP1 output froman external device.

As illustrated in part (a) of FIG. 4, at time tk1, the first sleepsignal SLP1 output from the external device rises from a low level to ahigh level. The external device outputs the high-level first sleepsignal SLP1 to the drive circuit 17 in the first memory macro 11 inorder to switch the semiconductor storage device 10 from the sleep modeto the normal mode.

As illustrated in part (b) of FIG. 4, at time tk1, the driven sleepsignal SLPd output from the drive circuit 17 in the first memory macro11 changes from a low level to a high level. The drive circuit 17 in thefirst memory macro 11 improves the drive performance of the first sleepsignal SLP1 input from the external device to obtain a driven sleepsignal SLPd, and outputs the driven sleep signal SLPd to the gate of thefirst transistors Ta, the first delay circuits 31, and the sleepcancellation detecting circuit 18 in the first memory macro 11. Inaccordance with a high-level driven sleep signal SLPd, the firsttransistors Ta in the first memory macro 11 couple the virtual powersupply lines LK and the ground potential GND.

As illustrated in part (c) of FIG. 4, the first delayed sleep signalSLPt1 output from the first delay circuits 31 in the first memory macro11 changes from a low level to a high level. The first delay circuits 31in the first memory macro 11 delay the driven sleep signal SLPd inputfrom the drive circuits 17 by the delay time t1 to obtain a firstdelayed sleep signal SLPt1, and output the first delayed sleep signalSLPt1 to the gates of the second transistors Tb and the second delaycircuits 32 in the first memory macro 11. In accordance with ahigh-level first delayed sleep signal SLPt1, the second transistors Tbin the first memory macro 11 couple the virtual power supply lines LKand the ground potential GND.

As illustrated in part (d) of FIG. 4, the second delayed sleep signalSLPt2 output from the second delay circuits 32 in the first memory macro11 changes from a low level to a high level. The second delay circuits32 in the first memory macro 11 delay the first delayed sleep signalSLPt1 input from the first delay circuits 31 by the delay time t1 toobtain a second delayed sleep signal SLPt2, and output the seconddelayed sleep signal SLPt2 to the gates of the third transistors Tc andthe third delay circuits 33 in the first memory macro 11. In accordancewith a high-level second delayed sleep signal SLPt2, the thirdtransistors Tc in the first memory macro 11 couple the virtual powersupply lines LK and the ground potential GND.

As illustrated in part (e) of FIG. 4, the third delayed sleep signalSLPt3 output from the third delay circuits 33 in the first memory macro11 changes from a low level to a high level. The third delay circuits 33in the first memory macro 11 delay the second delayed sleep signal SLPt2input from the second delay circuits 32 by the delay time t1 to obtain athird delayed sleep signal SLPt3, and output the third delayed sleepsignal SLPt3 to the gates of the fourth transistors Td and the sleepcancellation detecting circuit 18 in the first memory macro 11.

In accordance with a high-level third delayed sleep signal SLPt3, thefourth transistors Td in the first memory macro 11 couple the virtualpower supply lines LK and the ground potential GND. When the high-leveldriven sleep signal SLPd is input and then the third delayed sleepsignal SLPt3 output from the third delay circuits 33 changes from a lowlevel to a high level, the sleep cancellation detecting circuit 18 inthe first memory macro 11 outputs a high-level second sleep signal SLP2indicating, for example, the normal mode to the second memory macro 12.

The first memory macro 11 delays a high-level first sleep signal SLP1indicating, for example, the normal mode, which is input from anexternal device, by the delay time t3 (=3×t1) and detects that thevirtual power supply lines LK and the ground potential GND are coupledby the first to fourth transistors Ta to Td in the first memory macro 11turning on. Then, the first macro 11 outputs a high-level second sleepsignal SLP2 indicating, for example, the normal mode to the secondmemory macro 12.

As illustrated in part (f) of FIG. 4, at time tk3, a third sleep signalSLP3 output from the sleep cancellation detecting circuit 18 in thesecond memory macro 12 changes from a low level to a high level. Asillustrated in part (g) of FIG. 4, at time tk4, a fourth sleep signalSLP4 output from the sleep cancellation detecting circuit 18 in thethird memory macro 13 changes from a low level to a high level.

The second memory macro 12 delays a high-level second sleep signal SLP2indicating, for example, the normal mode, which is input from the firstmemory macro 11, by the delay time t3 (=3×t1) and outputs a high-levelthird sleep signal SLP3 indicating, for example, the normal mode to thethird memory macro 13 after detecting that the virtual power supplylines LK and the ground potential GND are coupled by the first to fourthtransistors Ta to Td in the second memory macro 12 turning on.

The third memory macro 13 delays a high-level third sleep signal SLP3indicating, for example, the normal mode, which is input from the secondmemory macro 12, by the delay time t3 (=3×t1) and outputs a high-levelfourth sleep signal SLP4 indicating, for example, the normal mode to thefourth memory macro 14 after detecting the virtual power supply lines LKand the ground potential ND are coupled by the first to fourthtransistors Ta to Td in the third memory macro 13 turning on.

When a high-level first sleep signal SLP1 indicating, for example, thenormal mode is input to the first memory macro 11, the first to fourthmemory macros 11 to 14 sequentially start switching from the sleep modeto the normal mode with the delay time t3 (=3×t1).

The sleep cancellation detecting circuit 18 detects the third delayedsleep signal SLPt3 output from the virtual power control circuit 23 inthe first memory cell array unit M1. The fourth transistor Td in thefirst memory cell array unit M1 determines whether or not the virtualpower supply line LK and the ground potential GND are coupled. When ahigh-level third delayed sleep signal SLPt3 is input, the sleepcancellation detecting circuit 18 outputs a high-level second sleepsignal SLP2 indicating, for example, the normal mode to the sequentsecond memory macro 12.

The configuration of the first memory cell array unit M1 may besubstantially the same as or similar to the configuration of the secondto n-th memory cell array units M2 to Mn. When the fourth transistor Tdin the first memory cell array unit M1 is turned on, the fourthtransistors Td in the second to n-th memory cell array units M2 to Mnmay also be turned on.

The sleep cancellation detecting circuit 18 determines whether or notthe first to fourth transistors Ta to Td of the virtual power controlcircuits 23 included in the first to n-th memory cell array units M1 toMn are turned on. The connection between the virtual power supply linesLK and the ground potential GND may be detected.

After return current becomes substantially a maximum in a given memorymacro, the mode of the subsequent memory macro is switched from thesleep mode to the normal mode. The return current in the semiconductorstorage device 10 is lower than that when the first to fourth memorymacros 11 to 14 are switched from the sleep mode to the normal modecontemporaneously, and the decrease in the power supply voltage Vcc maybe reduced.

FIG. 5 illustrates an exemplary memory macro. A driven sleep signal SLPdoutput from a drive circuit 17 is input to a virtual power controlcircuit 23 in a first memory cell array unit M1. A third delayed sleepsignal SLPt3 output from the virtual power control circuit 23 in thefirst memory cell array unit M1 is output to a virtual power controlcircuit 23 in the subsequent second memory cell array unit M2. In firstto n-th memory cell array units M1 to Mn, a third delayed sleep signalSLPt3 output from a given memory cell array unit is supplied to thesubsequent memory cell array unit. The third delayed sleep signal SLPt3output from the last n-th memory cell array unit Mn is supplied to thesleep cancellation detecting circuit 18.

In the first to n-th memory cell array units M1 to Mn in each memorymacro, after the first to fourth transistors Ta to Td in the virtualpower control circuit 23 included in a given memory cell array unit areturned on, the first to fourth transistors Ta to Td in the virtual powercontrol circuit 23 included in the subsequent memory cell array unit maybe turned on.

In the first to n-th memory cell array units M1 to Mn, when the delaytime t3 elapses since a given memory cell array unit starts switchingfrom the sleep mode to the normal mode, the subsequent memory cell arrayunit starts switching from the sleep mode to the normal mode.

The first to n-th memory cell array units M1 to Mn sequentially startswitching from the sleep mode to the normal mode. When the first tofourth transistors Ta to Td in the last n-th memory cell array unit Mnare turned on, the sleep cancellation detecting circuit 18 outputssecond to fourth sleep signals SLP2 to SLP4, which are at a high level,to the subsequent memory macro.

The virtual power control circuit 23 is supplied with the third delayedsleep signal SLPt3 output from the virtual power control circuit 23 inthe preceding memory cell array unit. The sleep cancellation detectingcircuit 18 detects the voltage level of the third delayed sleep signalSLPt3 output from the virtual power control circuit 23 in the last n-thmemory cell array unit Mn.

After the first to fourth transistors Ta to Td in a given memory cellarray unit are turned on, the first to fourth transistors Ta to Td inthe subsequent memory cell array unit may be turned on. After the firstto fourth transistors Ta to Td in the last n-th memory cell array unitMn are turned on, the subsequent memory macro starts switching from thesleep mode to the normal mode.

After return current becomes substantially a maximum in each of thememory cell array units M1 to Mn, the subsequent memory cell array unitstarts switching from the sleep mode to the normal mode. The returncurrent in the semiconductor storage device 10 may be reduced, and thedecrease in the power supply voltage Vcc may be reduced.

FIG. 6 illustrates an exemplary memory macro. A first memory macro 11includes a drive circuit 17, first to n-th memory cell array units M1 toMn, a sleep cancellation detecting circuit 18, an internal circuit unit50, and an input/output unit 51.

The first memory macro 11 illustrated in FIG. 6 may be included in thesemiconductor storage device 10 illustrated in FIG. 1. The first memorymacro 11 is switched to the normal mode or the sleep mode in accordancewith a first sleep signal SLP1 input from an external device (notillustrated).

The drive circuit 17 includes a first inverter circuit 20 a and a secondinverter circuit 20 b, which are coupled in series. A first sleep signalSLP1 is input to the drive circuit 17 from an external device (notillustrated). In the drive circuit 17, the first sleep signal SLP1 issupplied to the second inverter circuit 20 b which has high drivingperformance to obtain a driven sleep signal SLPd, and the driven sleepsignal SLPd is output to the first to n-th memory cell array units M1 toMn and the sleep cancellation detecting circuit 18.

Each of the memory cell array units M1 to Mn includes a virtual powercontrol circuit 23, a memory cell array 24, and an N-channel MOStransistor T1 serving as a low-potential power supply boosting circuit.The virtual power control circuit 23 controls the voltage level of avirtual power supply line LK, which is, for example, a low-potentialpower supply voltage of the memory cell array 24. In the normal mode,the virtual power control circuit 23 couples the virtual power supplyline LK to a ground potential GND. The memory cell array 24 is suppliedwith a power supply voltage Vcc as a high-potential power supplyvoltage, and is coupled to the ground potential GND as a low-potentialpower supply voltage. In the sleep mode, the virtual power controlcircuit 23 controls the voltage level of the virtual power supply lineLK to a threshold voltage of the N-channel MOS transistor T1. The memorycell array 24 is supplied with the power supply voltage Vcc as ahigh-potential power supply voltage and is also supplied with, as alow-potential power supply voltage, a voltage obtained by boosting theground potential GND by the threshold voltage of the N-channel MOStransistor T1.

In the sleep mode, a power supply voltage that is lower than that in thenormal mode by the threshold voltage of the N-channel MOS transistor T1is supplied to the memory cell array 24, resulting in lower powerconsumption.

The configuration of the virtual power control circuit 23 included inthe first memory cell array unit M1 is substantially the same as orsimilar to the configuration of the virtual power control circuit 23illustrated in FIG. 1. For example, as illustrated in FIG. 3, thevirtual power control circuit 23 included in the first memory cell arrayunit M1 includes first to fourth transistors Ta to Td and first to thirddelay circuits 31 to 33. The first to fourth transistors Ta to Td may beN-channel MOS transistors, and the transistor sizes of the first tofourth transistors Ta to Td may increase in this order.

The driven sleep signal SLPd output from the drive circuit 17 issupplied to the gate of the first transistor Ta, and is also supplied tothe first delay circuit 31. A drain of the first transistor Ta iscoupled to the virtual power supply line LK of the memory cell array 24,and a source of the first transistor Ta is coupled to the groundpotential GND. In accordance with the driven sleep signal SLPd outputfrom the drive circuit 17, the first transistor Ta connects ordisconnects the virtual power supply line LK and the ground potentialGND.

In the normal mode, for example, when a high-level driven sleep signalSLPd is input, the first transistor Ta is turned on and couples thevirtual power supply line LK and the ground potential GND. In the sleepmode, when a low-level driven sleep signal SLPd is input, the firsttransistor Ta is turned off and disconnects the virtual power supplyline LK and the ground potential GND.

The first delay circuit 31 includes a first inverter circuit 35 a and asecond inverter circuit 35 b, which are coupled in series. When a drivensleep signal SLPd is input from the drive circuit 17, the first delaycircuit 31 delays the driven sleep signal SLPd by the delay time t1 toobtain a first delayed sleep signal SLPt1, and outputs the first delayedsleep signal SLPt1 to the gate of the second transistor Tb and thesecond delay circuit 32.

A drain of the second transistor Tb is coupled to the virtual powersupply line LK, and a source of the second transistor Tb is coupled tothe ground potential GND. The first delayed sleep signal SLPt1 outputfrom the first delay circuit 31 is supplied to a gate of the secondtransistor Tb. In accordance with the first delayed sleep signal SLPt1output from the first delay circuit 31, the second transistor Tbconnects or disconnects the virtual power supply line LK and the groundpotential GND.

The second transistor Tb operates behind the delay time t1 from theoperation timing of the first transistor Ta. In the normal mode, forexample, when a high-level first delayed sleep signal SLPt1 is input,the second transistor Tb is turned on and couples the virtual powersupply line LK and the ground potential GND. In the sleep mode, forexample, when a low-level first delayed sleep signal SLPt1 is input, thesecond transistor Tb is turned off and disconnects the virtual powersupply line LK and the ground potential GND.

The second delay circuit 32 includes a first inverter circuit 36 a and asecond inverter circuit 36 b, which are coupled in series. The seconddelay circuit 32 delays the first delayed sleep signal SLPt1 input fromthe first delay circuit 31 by the delay time t1 to obtain a seconddelayed sleep signal SLPt2, and outputs the second delayed sleep signalSLPt2 to the gate of the third transistor Tc and the third delay circuit33.

A drain of the third transistor Tc is coupled to the virtual powersupply line LK, and a source of the third transistor Tc is coupled tothe ground potential GND. The second delayed sleep signal SLPt2 outputfrom the second delay circuit 32 is supplied to a gate of the thirdtransistor Tc. In accordance with the second delayed sleep signal SLPt2input from the second delay circuit 32, the third transistor Tc connectsor disconnects the virtual power supply line LK and the ground potentialGND.

The third transistor Tc operates behind the delay time t1 from theoperation timing of the second transistor Tb. The third transistor Tcoperates behind the delay time t2 (−2×t1) from the operation timing ofthe first transistor Ta.

In the normal mode, for example, when a high-level second delayed sleepsignal SLPt2 is input, the third transistor Tc is turned on and couplesthe virtual power supply line LK and the ground potential GND. In thesleep mode, for example, when a low-level second delayed sleep signalSLPt2 is input, the third transistor Tc is turned off and disconnectsthe virtual power supply line LK and the ground potential GND.

The third delay circuit 33 includes a first inverter circuit 37 a and asecond inverter circuit 37 b, which are coupled in series. The thirddelay circuit 33 delays the second delayed sleep signal SLPt2 outputfrom the second delay circuit 32 by the delay time t1 to obtain a thirddelayed sleep signal SLPt3, and outputs the third delayed sleep signalSLPt3 to the gate of the fourth transistor Td.

A drain of the fourth transistor Td is coupled to the virtual powersupply line LK, and a source of the fourth transistor Td is coupled tothe ground potential GND. The third delayed sleep signal SLPt3 outputfrom the third delay circuit 33 is supplied to a gate of the fourthtransistor Td. In accordance with the third delayed sleep signal SLPt3output from the third delay circuit 33, the fourth transistor Tdconnects or disconnects the virtual power supply line LK and the groundpotential GND.

The fourth transistor Td operates behind the delay time t1 from theoperation timing of the third transistor Tc. The fourth transistor Tdoperates behind the delay time t3 (=3×t1) from the operation timing ofthe first transistor Ta.

The delay time t3 may correspond to the time period from when the firstmemory macro 11 starts switching from the sleep mode to the normal modeto when return current flowing during the switching from the sleep modeto the normal mode becomes substantially maximum by the first to fourthtransistors Ta to Td turning on.

In the normal mode, for example, when a high-level third delayed sleepsignal SLPt3 is input, the fourth transistor Td is turned on and couplesthe virtual power supply line LK and the ground potential GND. In thesleep mode, for example, when a low-level third delayed sleep signalSLPt3 is input, the fourth transistor Td is turned off and disconnectsthe virtual power supply line LK and the ground potential GND.

The virtual power control circuit 23 sequentially delays the high-leveldriven sleep signal SLPd input from the drive circuit 17 using the firstto third delay circuits 31 to 33 to turn on the second to fourthtransistors Tb to Td with the delay times t1, t2 (=2×t1), and t3(=3×t1), respectively, so that the virtual power supply line LK and theground potential GND are coupled to each other.

The virtual power control circuit 23 turns on the first to fourthtransistors Ta to Td sequentially when the sleep mode is switched to thenormal mode. Therefore, the conductance is increased stepwise andcurrent flow from the virtual power supply line LK to the groundpotential GND is facilitated.

The virtual power control circuit 23 decreases stepwise the voltagelevel of the virtual power supply line LK to the ground potential GNDduring the switching from the sleep mode to the normal mode, andincreases stepwise the power supply voltage from the minimum powersupply voltage for the sleep mode to the normal power supply voltage forthe normal mode (which is greater than the minimum power supplyvoltage), resulting in an increase in the switching time. Thus, themaximum value of return current may be reduced.

The memory cell array 24 in the first memory cell array unit M1 includesa plurality of memory cells arranged in a matrix (not illustrated). Thememory cells store data of “1” or “0”, and the data is written into orread from the memory cells. The power supply voltage Vcc and the voltageof the virtual power supply line LK are supplied to each of the memorycells as a high-potential power supply voltage and a low-potential powersupply voltage, respectively.

A drain and a gate of the N-channel MOS transistor T1 in the firstmemory cell array unit M1 are coupled to the virtual power supply lineLK of the memory cell array 24, and a source of the N-channel MOStransistor T1 is coupled to the ground potential GND. The N-channel MOStransistor T1 connects or disconnects the virtual power supply line LKand the ground potential GND using the virtual power control circuit 23.

When the virtual power supply line LK and the ground potential GND aredisconnected by the virtual power control circuit 23, a standby currentof the memory cell array 24 in the sleep mode is supplied to theN-channel MOS transistor T1 in the first memory cell array unit M1.Thus, the gate voltage is set around the threshold voltage so that theN-channel MOS transistor T1 is turned on. The voltage level of thevirtual power supply line LK becomes substantially equal to thethreshold voltage of the N-channel MOS transistor T1.

When the virtual power supply line LK and the ground potential GND arecoupled by the virtual power control circuit 23, the drain and gate ofthe N-channel MOS transistor T1 are coupled to the ground potential GNDto turn off the N-channel MOS transistor T1. The voltage level of thevirtual power supply line LK becomes substantially equal to the groundpotential GND.

The N-channel MOS transistor T1 is turned on in the sleep mode, and thevoltage level of the virtual power supply line LK becomes close to thethreshold voltage of the N-channel MOS transistor T1. The N-channel MOStransistor T1 is turned off in the normal mode, and the voltage level ofthe virtual power supply line LK becomes substantially equal to theground potential GND.

In the second to n-th memory cell array units M2 to Mn, the virtualpower control circuits 23 may not output the third delayed sleep signalSLPt3 supplied from the third delay circuits 33 to the sleepcancellation detecting circuit 18. Other configuration of the virtualpower control circuits 23 in the second to n-th memory cell array unitsM2 to Mn may be substantially the same as or similar to theconfiguration of the virtual power control circuit 23 in the firstmemory cell array unit M1.

In the first to n-th memory cell array units M1 to Mn, the first tofourth transistors Ta to Td included in the virtual power controlcircuits 23 may operate at substantially the same time. The thirddelayed sleep signal SLPt3, which indicates that the first to fourthtransistors Ta to Td included in the virtual power control circuit 23 ineach of the memory cell array units M1 to Mn are turned on, may beoutput from the virtual power control circuit 23 in the first memorycell array unit M1.

As illustrated in FIG. 6, the sleep cancellation detecting circuit 18 inthe first memory macro 11 includes a NAND circuit 40 and an invertercircuit 41. The driven sleep signal SLPd output from the drive circuit17 and the third delayed sleep signal SLPt3, which is obtained bydelaying the driven sleep signal SLPd output from the virtual powercontrol circuit 23 in the first memory cell array unit M1 by the delaytime t3, are input to the NAND circuit 40. When the driven sleep signalSLPd and the third delayed sleep signal SLPt3 are at a high level, theNAND circuit 40 outputs a low-level control completion signal Sk to theinverter circuit 41, the internal circuit unit 50, and the input/outputunit 51.

The inverter circuit 41 receives a control completion signal Sk from theNAND circuit 40. The inverter circuit 41 inverts the control completionsignal Sk to obtain a second sleep signal SLP2, and outputs the secondsleep signal SLP2 to the second memory macro 12.

When the first to fourth transistors Ta to Td of the virtual powercontrol circuits 23 included in the first to n-th memory cell arrayunits M1 to Mn are turned on, in response to the high-level thirddelayed sleep signal SLPt3 output from the virtual power control circuit23 in the first memory cell array unit M1, the sleep cancellationdetecting circuit 18 outputs a low-level control completion signal Sk tothe internal circuit unit 50 and the input/output unit 51, and furtheroutputs a high-level second sleep signal SLP2 indicating the normal modeto the second memory macro 12.

When the first to fourth transistors Ta to Td of the virtual powercontrol circuits 23 included in the first to n-th memory cell arrayunits M1 to Mn are turned off, in accordance with a low-level drivensleep signal SLPd output from the drive circuit 17, the sleepcancellation detecting circuit 18 outputs a high-level controlcompletion signal Sk to the internal circuit unit 50 and theinput/output unit 51, and further outputs a low-level second sleepsignal SLP2 to the second memory macro 12.

The internal circuit unit 50 includes an internal circuit 52 and a powercontrol transistor T3. The internal circuit 52 may be a peripheralcircuit such as a decoder for selecting a word line and a bit line. Thepower control transistor T3 may be a P-channel MOS transistor. A sourceof the power control transistor T3 is coupled to a power supply line LVand a drain of the power control transistor T3 is coupled to theinternal circuit 52. A control completion signal Sk from the sleepcancellation detecting circuit 18 is supplied to a gate of the powercontrol transistor T3. In accordance with the control completion signalSk, the power control transistor T3 supplies a power supply voltage Vccto the internal circuit 52 or disconnects the supply of the power supplyvoltage Vcc.

In accordance with a high-level control completion signal Sk, the powercontrol transistor T3 is turned off and disconnects the power supplyline LV and the internal circuit 52 so that the power supply voltage Vccis not supplied to the internal circuit 52. In accordance with alow-level control completion signal Sk, the power control transistor T3is turned on and couples the power supply line LV and the internalcircuit 52 so that the power supply voltage Vcc is supplied to theinternal circuit 52.

The input/output unit 51 includes an input/output circuit 53 and a powercontrol transistor T4. The input/output circuit 53 supplies a datasignal, an address signal, or the like to the memory cells. The powercontrol transistor T4 may be a P-channel MOS transistor. A source of thepower control transistor T4 is coupled to the power supply line LV and adrain of the power control transistor T4 is coupled to the input/outputcircuit 53. A control completion signal Sk from the sleep cancellationdetecting circuit 18 is supplied to a gate of the power controltransistor T4. In accordance with the control completion signal Sk, thepower control transistor T4 supplies the power supply voltage Vcc to theinput/output circuit 53 or disconnects the supply of the power supplyvoltage Vcc.

In accordance with a high-level control completion signal Sk, the powercontrol transistor T4 is turned off and disconnects the power supplyline LV and the input/output circuit 53 so that the power supply voltageVcc is not supplied to the input/output circuit 53. In accordance with alow-level control completion signal Sk, the power control transistor T4is turned on and couples the power supply line LV and the input/outputcircuit 53 so that the power supply voltage Vcc is supplied to theinput/output circuit 53.

The sleep cancellation detecting circuit 18 in the first memory macro 11starts to switch the first memory cell array unit M1 from the sleep modeto the normal mode. When detecting that the first to fourth transistorsTa to Td are turned on and that the return current becomes substantiallymaximum, for example, when the delay time t3 (=3×t1) has elapsed, thesleep cancellation detecting circuit 18 outputs a low-level controlcompletion signal Sk to the power control transistor T3 in the internalcircuit unit 50 and the power control transistor T4 in the input/outputunit 51 to start the power supply to the internal circuit 52 and theinput/output circuit 53.

In the subsequent memory macros 12 to 14, when the second to fourthsleep signals SLP2 to SLP4 are input from the preceding first to thirdmemory macros 11 to 13, respectively, as in the first memory macro 11,the sleep cancellation detecting circuits 18 start to switch the firstmemory cell array units M1 from the sleep mode to the normal mode. Whendetecting that the first to fourth transistors Ta to Td are turned onand that the return current becomes substantially maximum, for example,when the delay time t3 (=3×t1) has elapsed, the sleep cancellationdetecting circuits 18 output a low-level control completion signal Sk tothe power control transistors T3 in the corresponding internal circuitunits 50 and the power control transistors T4 in the correspondinginput/output units 51 to start the power supply to the internal circuits52 and the input/output circuits 53.

In each of the first to fourth memory macros 11 to 14, upon detectingthat the low-potential voltage to be applied to the memory cell arrays24, for example, the potential of the virtual power supply lines LK isdecreased stepwise to the power supply voltage for the normal mode bythe virtual power control circuits 23 during the switching from thesleep mode to the normal mode, the sleep cancellation detecting circuit18 supplies the power supply voltage Vcc to the internal circuit 52 andthe input/output circuit 53. Therefore, power supply noise may bereduced.

In each of the first to fourth memory macros 11 to 14, during the sleepmode, the sleep cancellation detecting circuit 18 stops the supply ofthe power supply voltage Vcc to the internal circuit 52 and theinput/output circuit 53, thereby the power consumption in the internalcircuit 52 and the input/output circuit 53 is reduced.

FIG. 7 illustrates an exemplary semiconductor device. In FIG. 7,elements that are substantially the same as the elements illustrated inFIGS. 1 to 6 are assigned the same reference numerals, and theexplanation may be omitted or reduced.

In a semiconductor device 60 illustrated in FIG. 7, first to fourthmemory macros 11 to 14 may control the supply of a power supply voltageVcc to first to fourth functional blocks B1 to B4 in accordance with acompletion signal Sk.

The semiconductor device 60 includes the first to fourth memory macros11 to 14, the first to fourth functional blocks B1 to B4, and first tofourth power control transistors T5 to T8. The first memory macro 11outputs, for example, the control completion signal Sk illustrated inFIG. 6, which is supplied from the NAND circuit 40 in the sleepcancellation detecting circuit 18 provided in the first memory macro 11,to the first power control transistor T5 as a second inverted sleepsignal BSLP2. The second memory macro 12 outputs the control completionsignal Sk supplied from the NAND circuit 40 in the sleep cancellationdetecting circuit 18 provided in the second memory macro 12 to thesecond power control transistor T6 as a third inverted sleep signalBSLP3.

The third memory macro 13 outputs the control completion signal Sksupplied from the NAND circuit 40 in the sleep cancellation detectingcircuit 18 provided in the third memory macro 13 to the third powercontrol transistor T7 as a fourth inverted sleep signal BSLP4. Thefourth memory macro 14 outputs the control completion signal Sk suppliedfrom the NAND circuit 40 in the sleep cancellation detecting circuit 18provided in the fourth memory macro 14 to the fourth power controltransistor T8 as a fifth inverted sleep signal BSLP5.

The first power control transistor T5 may be a P-channel MOS transistor.A source of the first power control transistor T5 is coupled to thepower supply line LV and a drain of the first power control transistorT5 is coupled to the first functional block B1. A second inverted sleepsignal BSLP2 from the first memory macro 11 is supplied to a gate of thefirst power control transistor T5. In accordance with the secondinverted sleep signal BSLP2, the first power control transistor T5supplies the power supply voltage Vcc to the first functional block B1.

During the sleep mode, for example, when a high-level second invertedsleep signal BSLP2 is input, the first power control transistor T5 doesnot supply the power supply voltage Vcc to the first functional blockB1. During the normal mode, for example, when a low-level secondinverted sleep signal BSLP2 is input, the first power control transistorT5 supplies the power supply voltage Vcc to the first functional blockB1.

The first power control transistor T5 stops the supply of the powersupply voltage Vcc to the first functional block B1 in the sleep mode.The first power control transistor T5 supplies the power supply voltageVcc to the first functional block B1 in the normal mode.

The second power control transistor T6 may be a P-channel MOStransistor. A source of the second power control transistor T6 iscoupled to the power supply line LV and a drain of the second powercontrol transistor T6 is coupled to the second functional block B2. Athird inverted sleep signal BSLP3 from the second memory macro 12 issupplied to a gate of the second power control transistor T6. Inaccordance with the third inverted sleep signal BSLP3, the second powercontrol transistor T6 supplies the power supply voltage Vcc to thesecond functional block B2.

During the sleep mode, for example, when a high-level third invertedsleep signal BSLP3 is input, the second power control transistor T6 doesnot supply the power supply voltage Vcc to the second functional blockB2. During the normal mode, for example, when a low-level third invertedsleep signal BSLP3 is input, the second power control transistor T6supplies the power supply voltage Vcc to the second functional block B2.

The second power control transistor T6 stops the supply of the powersupply voltage Vcc to the second functional block B2 in the sleep mode.The second power control transistor T6 supplies the power supply voltageVcc to the second functional block B2 in the normal mode.

The third power control transistor T7 is coupled to the third functionalblock B3, and the fourth power control transistor T8 is coupled to thefourth functional block B4. Other configuration of the third and fourthpower control transistors T7 and T8 may be substantially the same as orsimilar to the configuration of the first and second power controltransistors T5 and T6.

In each of the first to fourth memory macros 11 to 14, upon detectingthat the low-potential voltage (potential of the virtual power supplylines LK) to be applied to the memory cell arrays 24 has been decreasedstepwise to the power supply voltage for the normal mode by the virtualpower control circuits 23 during the switch from the sleep mode to thenormal mode, the sleep cancellation detecting circuit 18 supplies thepower supply voltage Vcc to the corresponding one of the functionalblocks B1 to B4. Therefore, power supply noise may be reduced.

In the semiconductor device 60, during the sleep mode, the sleepcancellation detecting circuits 18 in the first to fourth memory macros11 to 14 stop the supply of the power supply voltage Vcc to the first tofourth functional blocks B1 to B4, respectively, thereby the powerconsumption in the first to fourth functional blocks B1 to B4 beingreduced.

A semiconductor storage device may be controlled in accordance with achip enable signal CE.

FIG. 8 illustrates an exemplary memory macro. In FIG. 8, elements thatare substantially the same as the elements illustrated in FIGS. 1 to 7are assigned the same reference numerals, and the explanation may beomitted or reduced.

For example, the first to fourth memory macros 11 to 14 are selected inaccordance with a low-level chip enable signal CE. In accordance with ahigh-level chip enable signal CE (non-memory selection mode), the firstto fourth memory macros 11 to 14 stop their operation.

When the chip enable signal CE is at a low level (memory selection mode)and when the first to fourth sleep signals SLP1 to SLP4 are at a lowlevel (sleep mode), the first to fourth memory macros 11 to 14 enter aprohibition mode. When the chip enable signal CE is a high level(non-memory selection mode) and when the first to fourth sleep signalsSLP1 to SLP4 are at a high level (normal mode), the first to fourthmemory macros 11 to 14 enter a standby mode.

In the prohibition mode, the first to fourth memory macros 11 to 14 maywrite or read a data signal D under the condition where the power supplyvoltage to be applied has dropped. Therefore, the first to fourth memorymacros 11 to 14 may not write or read the data signal D correctly.

As illustrated in FIG. 8, the first memory macro 11 includes an inputcircuit 65 and a chip enable control circuit 66. The input circuit 65includes a write enable buffer 67 and an input buffer 68.

The write enable buffer 67 receives a write enable signal WE from anexternal device and a first synchronous chip enable signal CEs1 from thechip enable control circuit 66. In accordance with the first synchronouschip enable signal CEs1, the write enable buffer 67 latches the writeenable signal WE as a write enable signal WEa.

In accordance with a low-level first synchronous chip enable signal CEs1(memory selection mode), the write enable buffer 67 latches the writeenable signal WE as a write enable signal WEa. In accordance with ahigh-level first synchronous chip enable signal CEs1 (non-memoryselection mode), the write enable buffer 67 does not latch the writeenable signal WE.

The write enable buffer 67 may write the data signal D into the memorycell arrays 24 in the first to n-th memory cell array units M1 to Mn inaccordance with a low-level first synchronous chip enable signal CEs1.The write enable buffer 67 may not write the data signal D into thememory cell arrays 24 in the first to n-th memory cell array units M1 toMn in accordance with a high-level first synchronous chip enable signalCEs1.

The input buffer 68 receives an address signal ADD and a data signal Dfrom an external device and a first synchronous chip enable signal CEs1from the chip enable control circuit 66. In accordance with the firstsynchronous chip enable signal CEs1, the input buffer 68 latches theaddress signal ADD and the data signal D as an address signal ADDa and adata signal Da, respectively.

In accordance with a low-level first synchronous chip enable signal CEs1(memory selection mode), the input buffer 68 latches the address signalADD and the data signal D as an address signal ADDa and a data signalDa, respectively. In accordance with a high-level first synchronous chipenable signal CEs1 (non-memory selection mode), the input buffer 68 maynot latch the address signal ADD and the data signal D.

When the first synchronous chip enable signal CEs1 is at a low level(memory selection mode), a word line and a bit line (not illustrated)are selected in accordance with the write enable signal WEa latched inthe write enable buffer 67 and the address signal ADDa and data signalDa latched in the input buffer 68. Thus, the data signal D is writteninto or read from the first to n-th memory cell array units M1 to Mn.

When the first synchronous chip enable signal CEs1 is at a high level(non-memory selection mode), the data signal D may not be written intoor read from the first to n-th memory cell array units M1 to Mn.

The configuration of the second to fourth memory macros 12 to 14 may besubstantially the same as or similar to the configuration of the firstmemory macro 11.

The first to fourth memory macros 11 to 14 sequentially receive first tofourth sleep signal SLP1 to SLP4, respectively. The first to fourthsleep signals SLP1 to SLP4 are delayed by wire delay or the like. Duringthe switching between the sleep mode and the normal mode based on a chipenable signal CE supplied from an external device, the first to fourthmemory macros 11 to 14 may be switched to the prohibition mode orstandby mode, rather than the normal mode or sleep mode, because of thedelayed first to fourth sleep signals SLP1 to SLP4.

When the sleep mode is switched to the normal mode, the first to fourthmemory macros 11 to 14 may enter the prohibition mode because the chipenable signal CE becomes a low level (chip selection mode) before thefirst to fourth sleep signals SLP1 to SLP4 rise from the low level(sleep mode) to the high level (normal mode).

When the normal mode is switched to the sleep mode, the first to fourthmemory macros 11 to 14 may enter the standby mode because the chipenable signal CE becomes a high level (non-chip selection mode) beforethe first to fourth sleep signals SLP1 to SLP4 fall from the high level(normal mode) to the low level (sleep mode).

Each of the memory macros 11 to 14 may include the chip enable controlcircuit 66 that controls the input timing of a chip enable signal CEfrom an external device.

The chip enable control circuit 66 includes an AND circuit 70, a Dflip-flop (D-FF) circuit 71, an inverter circuit 72, and a NAND circuit73. The AND circuit 70 is supplied with a clock signal CLK from anexternal device and is also supplied with a first adjusted sleep signalSLPa1 from the NAND circuit 73. In accordance with the clock signal CLKand the first adjusted sleep signal SLPa1, the AND circuit 70 outputs afirst adjusted clock signal CLKa1 to a clock terminal CK of the D-FFcircuit 71.

When the clock signal CLK and the first adjusted sleep signal SLPa1 areat a high level, the AND circuit 70 outputs a high-level first adjustedclock signal CLKa1 to the clock terminal CK of the D-FF circuit 71. Whenthe first adjusted sleep signal SLPa1 becomes a high level (normalmode), the AND circuit 70 outputs the clock signal CLK to the clockterminal CK of the D-FF circuit 71 as the first adjusted sleep signalSLPa1.

A chip enable signal CE supplied from an external device is input to adata input terminal D of the D-FF circuit 71. The first adjusted clocksignal CLKa1 supplied from the AND circuit 70 is input to the clockterminal CK of the D-FF circuit 71.

When the first adjusted clock signal CLKa1 rises to a high level, theD-FF circuit 71 holds the chip enable signal CE and further outputs thechip enable signal CE to the input circuit 65 and the NAND circuit 73 asa first synchronous chip enable signal CEs1.

During the switching from the sleep mode to the normal mode, when thechip enable signal CE falls from the high level (non-chip selectionmode) to the low level (chip selection mode), the D-FF circuit 71outputs a low-level (chip selection mode) first synchronous chip enablesignal CEs1 to the input circuit 65 and the NAND circuit 73 inaccordance with the first adjusted clock signal CLKa1.

During the switching from the sleep mode to the normal mode, when thechip enable signal CE falls from the high level (non-chip selectionmode) to the low level (chip selection mode), the first adjusted clocksignal CLKa1 is not input and the D-FF circuit 71 maintains the outputof the high-level (non-chip selection mode) first synchronous chipenable signal CEs1.

During the switching from the sleep mode to the normal mode, even when alow-level (chip selection mode) chip enable signal CE is input, the D-FFcircuit 71 does not output the low-level (chip selection mode) firstsynchronous chip enable signal CEs1 to the input circuit 65 or the NANDcircuit 73 until the first adjusted clock signal CLKa1 is input.

In accordance with a first sleep signal SLP1 supplied from an externaldevice, the inverter circuit 72 inverts the first sleep signal SLP1 toobtain a first logic sleep signal LSLP1, and outputs the first logicsleep signal LSLP1 to the NAND circuit 73.

The NAND circuit 73 is supplied with the first logic sleep signal LSLP1from the inverter circuit 72, and is also supplied with the firstsynchronous chip enable signal CEs1 from the D-FF circuit 71. When thefirst logic sleep signal LSLP1 and the first synchronous chip enablesignal CEs1 are at a high level, the NAND circuit 73 outputs a low-level(sleep mode) first adjusted sleep signal SLPa1 to the drive circuit 17and the AND circuit 70.

When the sleep mode is switched to the normal mode, for example, whenthe first sleep signal SLP1 changes from the low level (sleep mode) tothe high level (normal mode) in accordance with a high-level (non-chipselection mode) first synchronous chip enable signal CEs1, the NANDcircuit 73 also sets the first adjusted sleep signal SLPa1 from the lowlevel (sleep mode) to the high level (normal mode).

When the normal mode is switched to the sleep mode, since a low-level(chip selection mode) first synchronous chip enable signal CEs1 isinput, the NAND circuit 73 maintains the output of the high-level(normal mode) first adjusted sleep signal SLPa1 even when the firstsleep signal SLP1 changes from the high level (normal mode) to the lowlevel (sleep mode).

In accordance with a high-level (non-chip selection mode) firstsynchronous chip enable signal CEs1, the NAND circuit 73 causes thefirst adjusted sleep signal SLPa1 to fall from the high level (normalmode) to the low level (sleep mode).

When the sleep mode is switched to the normal mode, even when alow-level (chip selection mode) chip enable signal CE is input, the chipenable control circuit 66 may not output the low-level (chip selectionmode) first synchronous chip enable signal CEs1 to the input circuit 65until the clock signal CLK rises in accordance with a high-level (normalmode) first sleep signal SLP1.

When the clock signal CLK rises in accordance with a high-level (normalmode) first sleep signal SLP1, the chip enable control circuit 66outputs a low-level (chip selection mode) first synchronous chip enablesignal CEs1 to the input circuit 65.

When the normal mode is switched to the sleep mode, even when ahigh-level (non-chip selection mode) chip enable signal CE is input, thechip enable control circuit 66 may not output the high-level (non-chipselection mode) first synchronous chip enable signal CEs1 to the inputcircuit 65 until the clock signal CLK rises in accordance with alow-level (sleep mode) first sleep signal SLP1.

When the clock signal CLK rises in accordance with a low-level (sleepmode) first sleep signal SLP1, the chip enable control circuit 66outputs a high-level (non-chip selection mode) first synchronous chipenable signal CEs1 to the input circuit 65.

In each of the first to fourth memory macros 11 to 14, when the sleepmode is switched to the normal mode, the corresponding one of the firstto fourth sleep signals SLP1 to SLP4 rises to the high level (normalmode) and then the first synchronous chip enable signal CEs1 falls tothe low level (chip selection mode).

In each of the first to fourth memory macros 11 to 14, when the normalmode is switched to the sleep mode, the corresponding one of the firstto fourth sleep signals SLP1 to SLP4 falls to the low level (sleep mode)and then the first synchronous chip enable signal CEs1 rises to the highlevel (non-chip selection mode).

Therefore, the first to fourth memory macros 11 to 14 do not enter theprohibition mode or standby mode during the switching between the normalmode and the sleep mode.

In the embodiment described above, the semiconductor storage device 10includes the first to fourth memory macros 11 to 14. A semiconductorstorage device may include any number of memory macros. Furthermore,each memory macro may include any number of memory cell array units.

In the embodiment described above, the third delayed sleep signal SLPt3is supplied to the sleep cancellation detecting circuits 18. The firstdelayed sleep signal SLPt1 or the second delayed sleep signal SLPt2 maybe supplied.

In the embodiment described above, the third delayed sleep signal SLPt3output from the first memory cell array units M1 is supplied to thesleep cancellation detecting circuits 18. The third delayed sleep signalSLPt3 may be supplied from the second to n-th memory cell array units M2to Mn. In the embodiment described above, the N-channel MOS transistorsT1 are provided between the memory cell arrays 24 and the groundpotential GND so that the low-potential power supply voltage of thememory cell arrays 24 is increased to the threshold voltage of theN-channel MOS transistors T1 in the sleep mode, thereby achieving areduction in power consumption.

A high-potential power supply step-down circuit may be provided betweeneach of the memory cell arrays 24 and the power supply voltage Vcc. Thehigh-potential power supply step-down circuit includes two P-channel MOStransistors that are coupled in parallel. The high-potential powersupply voltage of the memory cell arrays 24 is decreased by thethreshold voltage of the P-channel MOS transistors in the sleep mode,thereby providing reduced power consumption.

The gate of one of the P-channel MOS transistors provided between eachof the memory cell arrays 24 and the power supply voltage Vcc is coupledto the drains of the first to fourth transistors Ta to Td in thecorresponding one of the virtual power control circuits 23. Ahigh-potential power supply voltage is coupled to the gate of the otherP-channel MOS transistor provided between the memory cell array 24 andthe power supply voltage Vcc.

The first to fourth transistors Ta to Td, which are N-channel MOStransistors, in each of the virtual power control circuits 23 may bereplaced by P-channel MOS transistors. The power supply voltage that iscoupled to the sources of the first to fourth transistors Ta to Td ineach of the virtual power control circuits 23 may be the power supplyvoltage Vcc instead of the ground potential GND.

FIG. 9 illustrates an exemplary a memory macro. Referring to FIG. 9, thegate of a P-channel MOS transistor provided between each of memory cellarrays 24 and the power supply voltage Vcc is coupled to the drains offirst to fourth transistors Ta to Td in a corresponding one of virtualpower control circuits 23.

As illustrated in FIG. 9, an inverter circuit 75 for inverting a drivensleep signal SLPd is provided between a drive circuit 17 and virtualpower control circuits 23 in first to n-th memory cell array units M1 toMn. An inverter circuit 76 for inverting a third delayed sleep signalSLPt3 is provided between the virtual power control circuit 23 in then-th memory cell array unit Mn and a sleep cancellation detectingcircuit 18.

A P-channel MOS transistor may be provided between each of the memorycell arrays 24 and the power supply voltage Vcc. In the sleep mode, thevoltage of the high-potential power supply of the memory cell arrays 24is reduced by the threshold voltage of the P-channel MOS transistors. AnN-channel MOS transistor may be provided between each of the memory cellarrays 24 and the ground potential GND. In the sleep mode, the voltageof the low-potential power supply of the memory cell arrays 24 isincreased by the threshold voltage of the N-channel MOS transistors,thereby providing reduced power consumption.

Since a power supply voltage that is lower by the threshold voltage ofthe transistors is applied to the memory cell arrays 24, powerconsumption is further reduced. In the embodiment described above, thefirst to fourth functional blocks B1 to B4 are supplied with the powersupply voltage Vcc through the first to fourth power control transistorsT5 to T8, respectively.

FIG. 10 illustrates an exemplary semiconductor device. In thesemiconductor device illustrated in FIG. 10, first to fourth functionalblocks B1 to B4 are coupled to the drains of first to fourth powercontrol transistors T5 to T8. The first to fourth functional blocks B1to B4 are supplied with a power supply voltage from the drains of thefirst to fourth power control transistors T5 to T8, which are coupled inparallel.

Since the first to fourth power control transistors T5 to T8 aresequentially turned on when the sleep mode is switched to the normalmode, impedance gradually decreases.

Since the impedance of the first to fourth power control transistors T5to T8 gradually decreases when the sleep mode is switched to the normalmode, the current supplied to the first to fourth functional blocks B1to B4 gradually increases. Therefore, when the sleep mode is switched tothe normal mode, the current flowing through the first to fourthfunctional blocks B1 to B4 is reduced to reduce power supply noise.

The first to fourth power control transistors T5 to T8 have anytransistor size. For example, when the first to fourth power controltransistors T5 to T8 have substantially the same transistor size, theimpedance of the first to fourth power control transistors T5 to T8,which are coupled in parallel, decreases in proportion to the number ofpower control transistors that are turned on among the first to fourthpower control transistors T5 to T8. Accordingly, the current flowingthrough the first to fourth functional blocks B1 to B4 increases inproportion to the number of power control transistors that are turned onamong the first to fourth power control transistors T5 to T8.

For example, as the transistor sizes of the first to fourth powercontrol transistors T5 to T8 increase in order, the impedance of thefirst to fourth power control transistors T5 to T8, which are coupled inparallel, slowly increases each time the first to fourth power controltransistors T5 to T8 are turned on. Accordingly, the current flowingthrough the first to fourth functional blocks B1 to B4 slowly increaseseach time the first to fourth power control transistors T5 to T8 areturned on.

In the embodiment described above, when the chip enable signal CE is ata low level (chip selection mode), the chip enable control circuit 66outputs a low-level (chip selection mode) first synchronous chip enablesignal CEs1 to the input circuit 65 after a high-level (normal mode)first sleep signal SLP1 is input and thereafter the clock signal CLKrises.

FIG. 11 illustrates an exemplary memory macro. A chip enable controlcircuit 66 illustrated in FIG. 11 may include a delay circuit 80 fordelaying a first synchronous chip enable signal CEs1, which is providedbetween a D-FF circuit 71 and a NAND circuit 73. Since the firstsynchronous chip enable signal CEs1 is delayed in the chip enablecontrol circuit 66, transition to the prohibition mode is reliablyprevented.

FIG. 12 illustrates an exemplary delay circuit. A delay circuit 80 aillustrated in FIG. 12 may the delay circuit 80 illustrated in FIG. 11.The delay circuit 80 a illustrated in FIG. 12 includes a delay unit 81,a NAND circuit 82, and an inverter circuit 83. The delay unit 81includes a series circuit having inverter circuits 85 to 88. The delayunit 81 delays a first synchronous chip enable signal CEs1 output fromthe D-FF circuit 71 to obtain a first synchronous chip enable signalCEs1 a, and outputs the first synchronous chip enable signal CEs1 a tothe NAND circuit 82.

The NAND circuit 82 is supplied with the first synchronous chip enablesignal CEs1 a from the delay unit 81, and is also supplied with thefirst synchronous chip enable signal CEs1 from the D-FF circuit 71. Whenthe first synchronous chip enable signals CEs1 and CEs1 a are at a highlevel, the NAND circuit 82 outputs a low-level logic signal S1 to theinverter circuit 83.

The inverter circuit 83 inverts the logic signal S1 output from the NANDcircuit 82 to obtain a first synchronous chip enable signal CEs1 c, andoutputs the first synchronous chip enable signal CEs1 c to the inputcircuit 65. The delay circuit 80 a delays the first synchronous chipenable signal CEs1 by an delay time of the delay unit 81 to obtain afirst synchronous chip enable signal CEs1 c, and outputs the firstsynchronous chip enable signal CEs1 c to the input circuit 65.

FIG. 13 illustrates an exemplary delay circuit. A delay circuit 80 billustrated in FIG. 13 may be the delay circuit 80 illustrated in FIG.13. The delay circuit 80 b illustrated in FIG. 13 includes a delay unit93 including D-FF circuits 90 to 92. The delay unit 93 receives a firstsynchronous chip enable signal CEs1 from the D-FF circuit 71 illustratedin FIG. 11. Then, after the clock signal CLK rises three times, thefirst synchronous chip enable signal CEs1 is output as a firstsynchronous chip enable signal CEs1 c to the input circuit 65.

Therefore, the delay circuit 80 b delays the first synchronous chipenable signal CEs1 by an delay time of the delay unit 93 to obtain afirst synchronous chip enable signal CEs1 c, and outputs the firstsynchronous chip enable signal CEs1 c to the input circuit 65.

Exemplary aspects of the present invention have now been described inaccordance with the above advantages. It will be appreciated that theseexamples are merely illustrative of the invention. Many variations andmodifications will be apparent to those skilled in the art.

What is claimed is:
 1. A circuit semiconductor storage devicecomprising: a plurality of memory macros coupled in series, each of theplurality of memory macros including a plurality of memory cell arrays;a high-potential power supply step-down circuit provided for each of theplurality of memory cell arrays, the high-potential power supplystep-down circuit provided between a high-potential power supply and arespective memory cell array, the high-potential power supply step-downcircuit being configured to couple the high-potential power supply tothe respective memory cell array in a normal mode and configured tocouple the respective memory cell array to a voltage level lower thanthe high-potential power supply in a sleep mode; a virtual power controlcircuit provided for each of the plurality of memory cell arrays, thevirtual power control circuit including a plurality of switches providedin parallel with the high-potential power supply step-down circuit, eachof the plurality of switches supplying an output to the high-potentialpower supply step-down circuit independent of every other one of theplurality of switches, the plurality of switches being configured to beturned on when a mode control signal indicates to switch from the sleepmode to the normal mode and configured to be turned off when a modecontrol signal indicates to switch from the normal mode to the sleepmode; and a sleep cancellation detecting circuit configured to receivethe mode control signal and to output a subsequent mode control signalto a subsequent memory macro subsequent to one of the plurality ofmemory macros when the mode control signal supplied to the plurality ofswitches of one of the plurality of memory cell arrays in the one of theplurality of memory macros indicates to switch from the sleep mode tothe normal mode.
 2. The circuit semiconductor storage device accordingto claim 1, wherein the mode control signal is contemporaneously inputto one of the plurality of switches of the plurality of the memory cellarrays.
 3. The circuit semiconductor storage device according to claim1, wherein, when the mode control signal is input to the plurality ofswitches sequentially, the sleep cancellation detecting circuit detectsa last mode control signal that is input last to the plurality ofswitches.
 4. The circuit semiconductor storage device according to claim1, wherein, when the mode control signal is input to the plurality ofswitches sequentially, a last mode control signal that is input last tothe plurality of switches is supplied to the subsequent memory macro,and wherein the sleep cancellation detecting circuit detects the lastmode control signal in a last memory macro of the plurality of memorymacros coupled in series.